Hmm tough one.
The great were
Glen Tilbrook @ Whelans
Lloyd Cole @ Vicar St
Dylan @ The Point
The *real bad* were
Glen Hansard @ Whelans
Grand Drive @ Whelans (Sat night, brutal crowd)
The "Promised much but disappointed" were
Morrissey @ the Ambassador
Aimee Mann & The National Stadium
The one gig that really surprised me was Coldplay @ the Point. I was expecting it to be poor but it rocked in a big way.

Three that come to mind are....Low at the Olympia, Natalie Merchant at the Olympia and Cathal Coughlan in the Shelter. Joe Pernice played a stormer at Vicar St but that might have been the end of 2001.....I'm trusting my memory on these, not always reliable.

Skylarking - Vicar St.
The Frames, Damian Rice, Gemma Hayse, Mundy, Paddy Casey, Kila, ...
I could go on and on and ...
The gig was outstanding. Never seen anything better ever, not just this year.
I for got the Mundy Gig in the Lobby this summer. Damian Rice turned up and played Guitar and Glenn Handsard was on Drums for a bit. Afterward Damian and Mundy were on the street outside busking away for over an hour, playing covers. Classic. I was at the Heinekin gig (Damian R - The Frames) b4 that and that is probably No.3